1. Field of the Invention
The present invention relates to a latching device, particularly to a latching device for vehicle seats, and more particularly to a latching device for vehicle seats foldable and lockable in either of a seat forming or a cargo carrying position.
2. Background and Material Information
In an automobile, such as a two door coupe and the like, it is desirable to include a seat having a backrest which is capable of folding between an upright seating position and a forwardly folded position permitting ingress and egress to and from a rear seat of the automobile. For safety considerations, it is also desirable, as well as mandated by federal regulations, that the backrest be lockable in the upright position.
In other vehicles, such as a station wagons, pick up trucks, and sport utility vehicles, it is desirable to include a seat which is capable of folding between a locked upright seating position and a forwardly folded position. In the forwardly folded position, the back of the seat is often used as a load carrying surface such that, once the seat is folded forwardly, the back of the seat can be used as an extension of the vehicle floor to carry loads other than passengers, such as cargo.
In order to accomplish such a function, it is necessary to provide a latching device for the seat back which can lock the backrest in the upright position for carrying passengers, and it is also desirable to lock the backrest in the cargo carrying position in order to maintain a stable surface for the cargo placed thereon during transportation.
Furthermore, in recent years such latching mechanisms for seat backs have been required by federal regulation to pass a crash test, i.e., the Federal Motor Vehicle Safety Standards Test Requirements (FMVSS Test Requirements). These FMVSS Test Requirements relate to conditions that a seatback latch would be subjected to in a vehicle crash situation. The loads on the seatback latching mechanism are much greater during a crash situation than the low loads that are present during normal operation of the seatback latching mechanism. In this regard, the test dummies and the seatback mass experience deceleration loads of 20-30 g""s during the tests. Accordingly, for seatback latching mechanisms of the type that the present invention is directed to, the dynamic load imparted to the latching mechanism from the seatback mounting arm may be 10,000 kg for a very short period of time. Thus, the latching mechanism must be designed to carry 100 times the normal load during the FMVSS testing without structural failure of the latching mechanism or disengagement of the latching mechanism during the crash test.
In a known device of this type, a backrest mounting arm is pivotally mounted to a mounting bracket to which a latching lever is pivotally mounted. The backrest mounting arm includes a pair of notches at a lower end thereof at positions defining the upright position of the backrest and the forwardly folded position, and the latching/release lever includes a latching portion to engage in a respective one of the notches to retain the backrest mounting arm in either one of the upright or forwardly folded positions. Furthermore, the latching/release lever includes pivoting feature for moving the latching portion out of the notch to permit pivotal movement of the backrest mounting arm. However, in such a device, during the crash tests, it has been observed that the entire load for resisting movement of the backrest mounting arm during the FMVSS test is carried by the pivot pin mounting the latching/release lever to the mounting bracket, which often causes shearing of the pivot pin. It has also been observed that the latching portion of the latching lever is sometimes deformed laterally out of engagement with the retaining notch in the lower end of the backrest mounting arm. Either of these situations will result in a failure of the device to pass the crash test. The present inventors has determined that the reason for these failures is that previous latch designs carried the total FMVSS loads through the same latch load path that carries the loads during normal operation. Accordingly, by the present invention, a latch design has been provided that will carry a significant portion of the very high FMVSS loads through a secondary load path, thus enabling the latch design to be significantly improved for normal operation.
Additionally, in pivoting seatbacks of this type, it is also important that, in use, the seatback does not xe2x80x9cchuckxe2x80x9d (i.e., vibrate back and forth as the automobile is driven) due to play in the latching mechanism. This xe2x80x9cchuckingxe2x80x9d is difficult to prevent because the radius from the seat back pivot to the latching mechanism is small, on the order of about 25-50 mm, and the radius from the seatback pivot to the top of the seatback where the xe2x80x9cchuckingxe2x80x9d is observed is very large, on the order of about 700-1000 mm. Thus, an extremely small clearance in the latching mechanism results in a very large movement in the seatback. Furthermore, wear of the latch components during the life of the automotive vehicle also results in an increase in the amount of xe2x80x9cchuckingxe2x80x9d.
In this regard, it has been observed that excessive xe2x80x9cchuckingxe2x80x9d has been a problem with previous latch designs.
Moreover, another important design consideration is the load required for operation of the latch release lever. Thus, other requirements are that the load necessary for operation of the release lever be low and the length of travel during operation be short. These parameters must also be consistent from vehicle to vehicle for the 100,000 to 500,000 vehicles in which the seatback latches are installed during manufacture each year. It should be noted that during normal operation of the seatback, the only loads that must be overcome to release the latch are (1) any biasing load on the seatback due to gravity, (2) any load resulting from a seatback biasing spring, and (3) any biasing load on the release lever resulting from a return spring. Typically during normal operation, the low loads carried from the seatback mounting arm through the latch pin to the release lever pivot connected to the vehicle body (e.g., by a mounting bracket) are about 100-150 kg. It has been observed that release lever loads for previous latch designs have been too high and vary significantly from vehicle to vehicle.
Additionally, with previous latch designs, the design of the latch had to be compromised for the normal operating functions (release lever effort and chucking) in order to meet the FMVSS Test Requirements. In this regard, previous latch designs included an angled face on the detent portion of the latch. However, if the angled face on the detent portion is too great, the latch will be disengaged during FMVSS testing due to the radial component of the 10,000 kg load that is applied through the backrest mounting arm. Thus, since the latching device of the previous latch designs must be configured in order to ensure that none of the production latches would become disengaged under FMVSS loads during testing, the angled face of the detent portion had to be reduced as low as possible to prevent release during testing.
On the other hand, with previous latch designs, when the angled face on the detent portion is reduced too greatly, release handle operating loads increased significantly and large variations in operations from latch to latch in high volume production may occur due to tolerance variations in components and during assembly. Furthermore, the amount of tolerance variation that can be taken up and/or the amount of wear during durability testing that can be taken up is greatly reduced. Thus, the result of such reduction of the angle face is that to (1) release handle loads increase significantly and are more inconsistent, and to (2) minimize xe2x80x9cchuckingxe2x80x9d, the tolerances of the latch components must be reduced significantly, thereby significantly increasing costs and manufacturing difficulty.
Accordingly, the present invention has been provided to overcome the above-noted disadvantages during FMVSS testing, plus to enhance the design, to meet the above-noted design requirements for normal operation, to provide a latching device that will permit smooth and efficient operation of the backrest to either the upright position or the forwardly folding position, and also to enable the latching device to withstand loads to pass the FMVSS Test Requirements. The resulting design allows lower, more consistent operating effort, minimum xe2x80x9cchucking of the backrest, weight reduction of the elements forming the latching device, and lower manufacturing and assembly costs.
According to one aspect of the present invention, the latching device of the present invention is configured with a detent portion having an angled face between the latch point and a face of a latching member provided on a release lever that is greater than that of previous latch designs, which results in minimal xe2x80x9cchuckingxe2x80x9d of the seat back during normal operation. The angled face of the detent portion is required due to the normal tolerance variation in the components of the latching device. Without the angled engagement between the detent portion and the latching member, the components would have to be designed for operation with the worst-case tolerances. In this case when the tolerances of the components stack up in the other direction, the detent portion and latching member would have a very large clearance, which would result in excessive seatback xe2x80x9cchuckingxe2x80x9d.
The angled face between the latch point and the latching member also results in zero latch clearance being maintained even when wear occurs during the life of the latch. The greater the angled face on the detent portion of the latch, the more variation in latch component tolerances, or the more wear during durability testing, can be accommodated with the latch construction of the present invention. Furthermore, the greater the angled face on the detent portion of the latch, the lower the release handle loads will be that are necessary to release the latch during normal operating conditions.
Accordingly, the latching device of the present invention is configured with a detent portion having an angled face between the latch point and a face of a latching member provided on a release lever designed to optimize the normal latch operation, which provides a primary load path that permits easy operation of the release handle with lower, more consistent loads, results in minimal xe2x80x9cchuckingxe2x80x9d of the seat back during normal operation, allows for increased tolerances in manufacture, and allows for more wear through the life of the latch while minimizing xe2x80x9cchuckingxe2x80x9d. Additionally, a load transfer abutment portion connected to the vehicle body is located adjacent to the detent portion and the latching member such that upon the application of a threshold load (such as a typical crash test load), the latching member is deflected into engagement with the load transfer abutment portion to provide a secondary load path for the much higher loads that must be carried during the crash condition.
Thus, during normal operation, the low loads, e.g., about 100-150 kg, are carried by the primary load path from the backrest mounting arm through the latching member to the release lever pivot attached to a mounting bracket secured to the vehicle body. The detent portion on the upper arm is angled to take up the tolerances in the components and also to reduce release efforts. With the present invention, this angle can be much greater because approximately 50% of the much higher loads that must be carried during the FMVSS testing are carried by the secondary load path through engagement of the latching member with the load transfer abutment portion secured to the vehicle body. However, the present invention can be configured to carry as much as 90-99% of the crash test load through the load transfer abutment portion secured to the vehicle body.
It should be noted that during FMVSS testing, the latching member of the latch device immediately deflects and engages the load transfer abutment portion secured to the vehicle body. The load transfer abutment portion has a zero degree angle relative to the direction of the load from the backrest mounting arm resulting from the crash test, and thus there is no radial component of the load. Therefore, friction between the latching member and the secondary load path transfer abutment portion prevents the latch from disengaging due to the force component resulting from the angled face of the detent portion for the normal load path.
Accordingly, as a result of the secondary load path that carries a high percentage of the high loads during the FMVSS testing, the latch components of the present invention can be configured with a greater angled face on the detent portion for normal operation without extremely close tolerances yet still prevent xe2x80x9cchuckingxe2x80x9d. Furthermore, the latch can be manufactured in high volume production yet have lower and much more consistent operator release handle forces without the concern that the latch will disengage when subjected to the very high FMVSS testing loads.
In another aspect of the present invention, the latching device includes a first bracket configured to be mounted to a support member, the first bracket including a load transfer abutment portion. A second bracket is pivotally mounted to the first bracket by a first pivot, the second bracket including at least one detent portion to retain the second bracket in a first position. A latching member is mounted on the first bracket and movable with respect thereto, the latching member extending adjacent the load transfer abutment portion and engagable with the at least one detent portion to retain the second bracket in the first position. Furthermore, a primary load path is defined between the first bracket, the second bracket and the latching member that carries normal loads associated with the second bracket, and a secondary load path is defined between the first bracket, the second bracket and the latching member that carries loads above a threshold load associated with the second bracket. Thus, components forming the latching device may be configured to have greater tolerances without increasing chucking of a seatback that may be connected to one of the first and second brackets and to provide reduced, more consistent release effort for disengagement of the latching member from the at least one detent portion while preventing inadvertent disengagement thereof during conditions above the threshold load.
In a further aspect of the present invention, the primary load path of the latching device is defined by the first bracket, the latching member, the detent portion, and the second bracket, and the secondary load path is defined by the first bracket, the load transfer abutment portion, the latching member, the detent portion, and the second bracket. Moreover, the load transfer abutment portion, the detent portion and the latching member are configured such that a load tending to cause relative pivoting of the first and second brackets urges the latching member toward a release position to aid disengagement of the latching member from the detent portion, and when the load reaches the threshold load, the latching member deflects to engage the load transfer abutment portion, such that when the threshold load is exceeded, a portion of the load is carried along the secondary load path, thereby preventing the latching member from movement out of engagement with the detent notch due to frictional engagement between the latching member and the load transfer abutment portion so that the second bracket is maintained in the first position.
In another aspect of the latching device of the present invention, the load transfer abutment portion on the first bracket is formed with a clearance relative to the latching member during normal operation to permit easy disengagement of the latching member from the detent portion upon actuation of the latching member to a release position, the clearance further being such that the latching member engages the load transfer abutment portion when deflected by the threshold load, which prevents the latching member from movement out of engagement with the detent portion so that the second bracket is maintained in the first position.
According to a further aspect of the present invention, the load transfer abutment portion in the first bracket is formed as an arcuate slot with two generally arcuate side walls concentric with a second pivot about which the latching member is movable, and the arcuate slot is sized to receive the latching member with the clearance during normal operation to permit easy disengagement of the latching member from the detent portion upon actuation of the latching member toward the release position, the clearance further being such that the latching member engages the load transfer abutment portion when deflected by the threshold load to defined the secondary load path. The clearance may be in the range of about 0.25 mm to about 1.25 mm, and preferably is about 0.5 mm.
In another aspect of the present invention, the at least one detent portion is formed as a detent notch in the second bracket. Furthermore, at least one side wall of the detent notch is configured to angle inwardly toward a bottom end of the detent notch, thereby absorbing greater tolerances of components of the latching device and providing a more consistent release effort for disengagement of the latching member from the detent portion, and the at least one side wall of the detent notch may have an arcuate configuration.
In a further aspect of the present invention, the latching member engages the arcuate side wall of the detent notch at a contact point such that a line L1 perpendicular to a tangent to the surface of the latching member at the contact point extends at an angle xcex1 with respect to a line C passing through a center of a second pivot of a release lever and a center of the latching member the angle xcex1 lying within the range of about 2xc2x0 to about 5xc2x0, and preferably about 3.5xc2x0. Furthermore, the arcuate side wall may be defined by a radius R1 representing the distance from the center of the second pivot of the release lever to the contact point between the side wall and the latch pin, and the center of the radius R1 is offset from the center of the second pivot such that the angle xcex1 is maintained in a range of about 2xc2x0 to about 5xc2x0, and preferably at about 3.5xc2x0.
According to another aspect of the present invention, both side walls of the detent notch angle inwardly toward the bottom of the detent notch, thereby absorbing greater tolerances of components of the latching device and providing a more consistent release effort for disengagement of the latching member from the detent portion. Moreover, both side walls of the detent notch may have an arcuate configuration.
In another aspect of the present invention, the latching member of the latching device is formed as a latch pin, and the latch pin may engage a side wall of the detent notch at a contact point such that a line L1 perpendicular to a tangent to the surface of the latch pin at the contact point extends at an angle xcex1 with respect to a line C passing through a center of a second pivot of a release lever and a center of the latch pin, the angle xcex1 lying within the range of about 2xc2x0 to about 5xc2x0, and preferably about 3.5xc2x0.
Additionally, the latching device may be provided for a backrest of a vehicle seat. Moreover, one of the first and second brackets may be mounted to the backrest, and the other of the first and second brackets may be mounted to the vehicle body.
In other aspects of the present invention, the latching member may be configured as a hook-shaped member fixed to the release lever or as a laterally extending portion of the release lever. Additionally, the load transfer abutment portion on the first bracket may be formed as a plurality of pins fixedly secured to the first bracket or as a notch portion provided to the first bracket.
In another aspect of the present invention, a third bracket configured generally as an allochiral pair to the first bracket may be provided, with the third bracket mounted such that the second bracket is positioned between the first and second brackets, and the secondary path carries 90% of the loads greater than the threshold value.
In a further aspect of the latching device of the present invention, a first bracket is configured to be mounted to a support member, the first bracket including a load transfer abutment portion. A second bracket is mounted for movement relative to the first bracket, the second bracket including at least one detent portion to retain the second bracket in a first position. Additionally, a latching member is mounted on the first bracket and movable with respect thereto, the latching member extending adjacent the load transfer abutment portion and engagable with the at least one detent portion to retain the second bracket in the first position. Accordingly, a primary load path is defined between the first bracket, the second bracket and the latching member that carries normal loads associated with the second bracket, and a secondary load path is defined between the first bracket, the second bracket and the latching member that carries loads above a threshold load associated with the second bracket. Thus, components forming the latching device may be configured to have greater tolerances without increasing chucking of a device that may be connected to one of the first and second brackets and to provide reduced, more consistent release effort for disengagement of the latching member from the at least one detent portion while preventing inadvertent disengagement thereof during conditions above the threshold load. Furthermore, the primary load path is defined by the first bracket, the latching member, the detent portion, and the second bracket, and the secondary load path is defined by the first bracket, the load transfer abutment portion, the latching member, the detent portion, and the second bracket.
According to a further aspect of the present invention, the load transfer abutment portion, the detent portion and the latching member are configured such that a load tending to cause relative movement of the first and second brackets urges the latching member toward a release position to aid disengagement of the latching member from the detent portion, and when the load reaches the threshold load, the latching member deflects to engage the load transfer abutment portion, such that when the threshold load is exceeded, a portion of the load is carried along the secondary load path, thereby preventing the latching member from movement out of engagement with the detent portion due to frictional engagement between the latching member and the load transfer abutment portion so that the second bracket is maintained in the first position.
In a further aspect of the present invention, the load transfer abutment portion on the first bracket is formed with a clearance relative to the latching member during normal operation to permit easy disengagement of the latching member from the detent portion upon actuation of the latching member to a release position, the clearance further being such that the latching member engages the load transfer abutment portion when deflected by the threshold load, which prevents the latching member from movement out of engagement with the detent portion so that the second bracket is maintained in the first position.
According to another aspect of the present invention, the load transfer abutment portion in the first bracket is formed as a slot with two side walls generally perpendicular to the direction in which the latching member is movable, and the slot is sized to receive the latching member with the clearance during normal operation to permit easy disengagement of the latching member from the detent portion upon actuation of the latching member toward the release position, the clearance further being such that the latching member engages the load transfer abutment portion when deflected by the threshold load to defined the secondary load path. The clearance may be about 0.25 mm to about 1.25 mm, and preferably about 0.5 mm.
In a further aspect of the present invention, the at least one detent portion is formed as a detent slot in the second bracket. Additionally, at least one side wall of the detent slot may angle inwardly toward a bottom end of the detent slot, thereby absorbing greater tolerances of components of the latching device and providing a more consistent release effort for disengagement of the latching member from the detent portion. Also, the latching member may engage the side wall of the detent slot at a contact point such that a line L1 perpendicular to a tangent to the surface of the latching member at the contact point extends at an angle xcex1 with respect to a line C passing through a center of a second pivot of a release lever and a center of the latching member the angle xcex1 lying within the range of about 2xc2x0 to about 5xc2x0, and preferably about 3.5xc2x0.
In other aspects of the present invention, a third bracket configured generally as an allochiral pair to the first bracket may be provided, with the third bracket mounted such that the second bracket is positioned between the first and second brackets, and the secondary path carries 90% of the loads greater than the threshhold value. Furthermore, the latching member may be mounted for sliding movement.
According to another aspect of the present invention, a latching device for a backrest of a vehicle seat is provided, the latching device including a mounting bracket configured to be mounted to a support member, the mounting bracket including a load transfer abutment portion. A backrest mounting arm is pivotally mounted to the mounting bracket by a first pivot; the backrest mounting arm including at least one detent notch to retain the backrest mounting arm in a first position. A release lever is pivotally mounted to the mounting bracket by a second pivot spaced from the first pivot, the release lever including a latching member fixed at a position spaced from the second pivot, with the latching member extending adjacent the load transfer abutment portion and engagable with the at least one detent notch to retain the backrest mounting arm in the first position. Thus, a primary load path is defined between the mounting bracket, the backrest mounting arm and the latching member that carries normal loads associated with the backrest mounting arm, and a secondary load path is defined between the mounting bracket, the backrest mounting arm and the latching member that carries loads above a threshold load associated with the backrest mounting arm. Thus, components forming the latching device may be configured to have greater tolerances without increasing chucking of a seatback that may be connected to the backrest mounting arm and to provide reduced release effort for disengagement of the latching member from the at least one detent portion while preventing inadvertent disengagement thereof during conditions above the threshold load.
In another aspect of the latching device for a backrest of a vehicle seat according to the present invention, the load transfer abutment portion, the detent notch and the latching member are configured such that a load tending to cause relative pivoting of the mounting bracket and backrest mounting arms urges the latching member toward a release position to aid disengagement of the latching member from the detent notch, and when the load reaches a threshold value, the latching member deflects to engage the load transfer abutment portion, thereby preventing the latching member from movement out of engagement with the detent notch due to frictional engagement between the latching member and the load transfer abutment portion so that the backrest mounting arm is maintained in the first position.
In a further aspect of the latching device for a backrest of a vehicle seat according to the present invention, the load transfer abutment portion on the mounting bracket is formed with a clearance relative to the latching member during normal operation to permit easy disengagement of the latching member from the detent notch upon actuation of the release lever, the clearance further being such that the latching member engages the load transfer abutment portion when deflected by the threshold load, which prevents the latching member from movement out of engagement with the detent notch so that the backrest mounting arm is maintained in the first position.
In another aspect of the latching device for a backrest of a vehicle seat according to the present invention, the load transfer abutment portion in the mounting bracket may be formed as an arcuate slot with two generally arcuate side walls concentric with the second pivot and sized to receive the latching member with the clearance during normal operation to permit easy disengagement of the latching member from the detent notch upon actuation of the release lever, the clearance further being such that the latching member engages the load transfer abutment portion when deflected by the threshold load. Additionally, the clearance may be about 0.25 mm to about 1.25 mm, and is preferably about 0.5 mm.
In another aspect of the latching device for a backrest of a vehicle seat according to the present invention, at least one side wall of the detent notch may angle inwardly toward a bottom end of the detent notch, thereby absorbing greater tolerances of components of the latching device and providing a more consistent release effort for disengagement of the latching member from the detent portion.
According to a further aspect of the latching device for a backrest of a vehicle seat of the present invention, the at least one side wall of the detent notch has an arcuate configuration. Moreover, the latching member may engage the arcuate side wall of the detent notch at a contact point such that a line L1 perpendicular to a tangent to the surface of the latch pin at the contact point extends at an angle xcex1 with respect to a line C passing through a center of the second pivot of the release lever and a center of the latching member, the angle xcex1 lying within the range of about 2xc2x0 to about 5xc2x0, and preferably about 3.5xc2x0.
Furthermore, both side walls of the detent notch may angle inwardly toward the bottom of the detent notch, thereby absorbing greater tolerances of components of the latching device and providing a more consistent release effort for disengagement of the latching member from the detent portion. Additionally, both side walls of the detent notch may have an arcuate configuration.
In an additional aspect of the the latching device according to the present invention, a third bracket configured generally as an allochiral pair to the first bracket may be provided, and the third bracket is mounted such that the second bracket is positioned between the first and second brackets, and the secondary path carries 90% of the loads greater than the threshhold value.